Just to clarify here. Its that we do reset the test instance when the live is reset. Its not that we ask people to decommission their live. Its actually more that we ask when a test instance is set for you site, you always use that test location. Many customers will use a subdomain for this purpose that they can point to another location if required, however yours is an odd case whereby you wish to use a port at the end of your URL for some reason.
The intention of this is to stop abuse of the test system by people who are trying to use these as live licenses. Something we have unfortunately come across in the past. Its certainly not to stop you testing, and if you do for some reason find that you absolutely have to change the test URL, just contact us and we can go through that with you. You don't need to decommission your main site, nor would we ever ask for you to do that.